Polymerizable bactericides, such as quaternary ammonium compound–based monomers, have been intensively studied as candidates for immobilizing antibacterial components on dental resin. However, they ...predominantly exhibit a bacteriostatic behavior, rather than bactericidal, as the immobilized components are left with insufficient molecular movement to disrupt the bacterial surface structure through contact-mediated action. In this study, we developed a novel strategy to increase the density of the immobilized bactericide and enhance its antibacterial/antibiofilm properties by combining a surface-grafting technique with electron beam irradiation. A solution of the quaternary ammonium compound–based monomer, 12-methacryloyloxydodecylpyridinium bromide (MDPB), was coated on polymethyl methacrylate (PMMA) resin specimens at the concentrations of 30, 50, and 80 wt%. The coated resins were subsequently exposed to 10 MeV of electron beam irradiation at 50 and 100 kGy, followed by thermal stabilization at 60 °C. The antibacterial effect was evaluated by inoculating a Streptococcus mutans suspension on the coated PMMA resin samples, which exhibited bactericidal effects even after 28 d of aging (P < 0.05, Tukey’s honestly significant difference test). Transmission electron microscopy and bacteriolytic activity evaluation revealed that the S. mutans cells had sustained membrane depolarization. Furthermore, the antibiofilm effects against S. mutans and bacteria collected from human saliva were assessed. The thickness and the percentage of membrane-intact cells of the S. mutans and multispecies biofilms formed on the MDPB-immobilized surfaces were significantly lower than the uncoated PMMA specimens, even after 28-d aging (P < 0.05, Tukey’s honestly significant difference test). Thus, the immobilization of antibacterial MDPB via electron beam irradiation induced rapid membrane depolarization, increasing membrane permeability and eventually causing cell death. Our strategy substantially enhances the antibacterial properties of the resinous materials and inhibits biofilm formation, therefore demonstrating significant potential for preventing infectious diseases in the oral environment.
An experimental cavity disinfectant (ACC) that is intended to be used for various direct and indirect restorations was prepared by adding an antibacterial monomer 12-methacryloyloxydodecylpyridinum ...bromide (MDPB) at 5% into 80% ethanol. The antibacterial effectiveness of ACC and its influences on the bonding abilities of resin cements were investigated. To examine the antibacterial activity of unpolymerized MDPB, the minimum inhibitory and bactericidal concentrations (MIC and MBC) were determined for Streptococcus mutans, Lactobacillus casei, Actinomyces naeslundii, Parvimonas micra, Enterococcus faecalis, Fusobacterium nucleatum, and Porphyromonas gingivalis. Antibacterial activities of ACC and the commercial cavity disinfectant containing 2% chlorhexidine and ethanol (CPS) were evaluated by agar disk diffusion tests through 7 bacterial species and by MIC and MBC measurement for S. mutans. The effects of ACC and CPS to kill bacteria in dentinal tubules were compared with an S. mutans–infected dentin model. Shear bond strength tests were used to examine the influences of ACC on the dentin-bonding abilities of a self-adhesive resin cement and a dual-cure resin cement used with a primer. Unpolymerized MDPB showed strong antibacterial activity against 7 oral bacteria. ACC produced inhibition zones against all bacterial species similar to CPS. For ACC and CPS, the MIC value for S. mutans was identical, and the MBC was similar with only a 1-step dilution difference (1:2). Treatment of infected dentin with ACC resulted in significantly greater bactericidal effects than CPS (P < 0.05, analysis of variance and Tukey’s honest significant difference test). ACC showed no negative influences on the bonding abilities to dentin for both resin cements, while CPS reduced the bond strength of the self-adhesive resin cement (P < 0.05). This study clarified that the experimental cavity disinfectant containing 5% MDPB is more effective in vitro than the commercially available chlorhexidine solution to eradicate bacteria in dentin, without causing any adverse influences on the bonding abilities of resinous luting cements.
An antibacterial monomer 12-methacryloyloxydodecylpyridinum bromide (MDPB)-containing experimental, chemically cured primer was prepared to develop a new resin-based root canal filling system. This ...study investigated the antibacterial effects of the MDPB-containing primer (experimental primer EP) against Enterococcus faecalis and assessed the in vitro bonding and sealing abilities of the filling system, consisting of EP and a Bis-GMA-based sealer resin. Antibacterial effects of EP were evaluated by contact with planktonic or adherent bacteria for 30 or 60 sec, and the viable bacterial number was counted. The antibacterial effects against E. faecalis in dentinal tubules were also assessed, according to a root canal infection model. Bonding and sealing abilities of the experimental filling system were examined by microtensile bond strength tests and leakage tests based on fluid filtration methods. Significantly greater reduction in viable bacteria in planktonic and adherent form was obtained by short-period contact with EP compared with the control primer (without MDPB) or with the proprietary (Epiphany) primer (p < .05). Significantly greater bactericidal effects of the EP inside the dentinal tubule of root, as opposed to the control primer or Epiphany primer, were confirmed according to a root canal infection model (p < .05), and 100% killing of E. faecalis could be obtained by the application of EP after irrigation with a 5% sodium hypochlorite solution. The experimental endodontic filling system demonstrated significantly greater bond strength to root dentin than Epiphany sealer system (Epiphany primer and Epiphany Root Canal Sealant; p < .05), showing formation of resin tags and a hybridized layer. Leakage tests clarified that the experimental system provided excellent sealing. This study confirmed that the MDPB-containing experimental antibacterial primer has the ability to effectively disinfect the root canal. Additionally, the experimental root canal filling system employing this primer and the Bis-GMA-based sealer resin is useful for achieving good sealing, suggesting its possible benefit for successful endodontic treatments.
Fetal surgery: a critical review Kitagawa, H.; Pringle, K. C.
Pediatric Surgery International,
04/2017, Letnik:
33, Številka:
4
Journal Article, Book Review
Recenzirano
Therapeutic fetal surgical procedures are predicated upon the ability to make an accurate fetal diagnosis. The earliest open fetal surgical procedures were introduced in the 1960s to treat Rh ...isoimmunisation. They were introduced when it became possible to predict impending fetal demise. Open procedures were abandoned when percutaneous approaches proved superior. The introduction of fetal ultrasound allowed the diagnosis of other congenital anomalies, some being amenable to fetal interventions. Open fetal surgical procedures were initially utilised, with significant maternal morbidity. For some anomalies, percutaneous approaches became favoured. In general, all of these procedures involved significant risks to the mother, to save a baby that was likely to die before or shortly after birth without fetal intervention. Fetal repair for myelomeningocele was a “sea change” in approach. The same maternal risks were taken to improve the quality of life of the affected fetus, not save its life. The completion of the “MOMs Trial” has occasioned a “tsunami” of centres in North America applying this approach. Others are attempting percutaneous repairs, with mixed results. This paper reviews the history of fetal surgery, focusing on the themes of the tension between accurate diagnosis and prognosis and open versus “minimally invasive” approaches.
Antimicrobial resistance in Staphylococcus aureus imposes a high disease burden. Both phenotypic and genotypic monitoring are key to understanding and containing emerging resistant strains.
...Phenotypic monitoring of emerging resistance in S. aureus and correlation of priority strain phenotypes with whole-genome sequencing (WGS) findings.
Antimicrobial susceptibility test results of >40,000 isolates from 213 participating hospitals from 2011 to 2019 were exported from the national Japan Nosocomial Infections Surveillance (JANIS) database. Longitudinal and geographic distribution and prevalence of distinct multi-drug resistance phenotypes (‘resistance profiles’) of S. aureus were examined among hospitals and prefectures. We further conducted a genome sequence analysis of strains with specific resistance profiles of concern.
The overall prevalence of meticillin-resistant S. aureus (MRSA) decreased from 40.3% to 35.1% from 2011 to 2019. However, among dozens of S. aureus resistance profiles, only one profile of a type of MRSA, exhibited a statistically significant increase in inpatient frequency, exceeding 10% during the nine years. This MRSA profile showed resistance to oxacillin, erythromycin and levofloxacin. Analysis of WGS results of S. aureus isolates with this phenotype revealed that most belonged to clonal complex 8, and all carried SCCmec IV, typical of community-acquired MRSA.
Tracking distinct resistance profiles deepened our understanding of the overall decrease in MRSA and led to recognition of the emergence of a new resistance phenotype. This study provides a model for future epidemiological research on antimicrobial resistance correlating multi-drug resistance phenotypes with selective genome sequencing, which can be applied to other bacterial species.
In this paper, we present petrography, K–Ar ages, whole-rock major- and trace-element concentrations, and Sr–Nd–Hf–Pb isotopic ratios of volcanic rocks from Debre Birhan area in the northernmost Main ...Ethiopian Rift (MER). The K–Ar ages of the mafic series range from 27 to 0.25Ma, and two felsic rocks yield ages of 0.93 and 0.23Ma. The mafic volcanics are classified into older and younger series based on their K–Ar ages. The Mg-numbers (Mg#<60) of both mafic series, along with low Ni and Cr contents, clearly indicate that these lavas have undergone fractionation en route to the surface. Geochemical and isotopic compositions of the older and younger mafic lavas indicate that crustal contamination did not play a significant role in the evolution of their magmas, hence reflect the geochemical characteristics of the sources. The older and younger mafic volcanic rocks display contrasting trace element and isotopic signatures. The older lavas have higher La/Nb, Zr/Nb, Ba/Nb and 87Sr/86Sri (0.70445–0.70681) and lower ԐHf (−2.58 to +6.01) and ԐNd (−1.25 to +3.43) and less radiogenic Pb isotopic ratios (206Pb/204Pbi=17.82–18.64, except TG-54=19.1) relative to the younger mafic lavas. Correlations among isotopic ratios and trace element concentrations provide evidence for the involvement of at least three major end-member components (C-1, C-2, and C-3) in the petrogenesis of these mafic lavas. The C-1 end-member component contributes dominantly to younger mafic lavas, and has isotopic composition similar to the common component ‘C’ deduced from oceanic basalts. The second end-member component (C-2) is represented by lavas near the transition between older and younger, and has isotopic composition similar to that of the seafloor basalts of the Red Sea and the Gulf of Aden. The third end-member component (C-3) is prominent in the older mafic series, and similar isotopically to Pan-African lithosphere. The younger felsic volcanic rocks generally have higher 87Sr/86Sri (0.70395–0.70689) than younger mafic series (0.70366–0.70454) but Nd, Hf and Pb isotopic ratios similar to those of the younger mafic lavas. The element concentrations and Sr, Nd, Hf and Pb isotopic compositions of the younger felsic rocks are explained by fractional crystallization of mafic melts in shallow-level magma chambers accompanied by limited assimilation of crustal material. Low degrees of partial melting of existing mafic underplate can account for the genesis of the least-differentiated (intermediate) lavas, but failed to explain highly evolved younger felsic rocks.
•Volcanic rocks in the study area ages range from 27 to 0.23Ma.•Mafic magmatism records the change of lithospheric involvement.•Three mantle end-members are identified in mafic lavas.•Felsic magmas were dominantly formed by fractional crystallization.
Mangroves can deliver important socio-economic benefits and store significant volumes of carbon along tropical to temperate coastlines, but the distribution is controlled by complex geomorphologic, ...hydrodynamic and salinity conditions, as well as human-related pressures. In the Mekong delta, the interaction of tide, wave and riverine hydrodynamic processes clearly impacts sedimentation and mangrove distribution. Extensive mangroves presently occur along the northeastern delta margin (Can Gio, located 40 km southeast of Ho Chi Minh City), in an embayed, back-barrier environment subject to the highest tidal range (c. 4 m) and away from major fluvial distributary channels. However, the development of the Can Gio mangrove system during the Holocene evolution of the Mekong delta is not fully understood. This study aims to constrain the sedimentary evolution of the back-barrier mangrove in Can Gio based on stratigraphic, palynological and geochronological analyses of sediment cores. Two deep borehole cores (15 and 30 m deep) and four short auger cores (up to 4 m deep) were taken at the modern mangrove to characterize a 20-km-long shore-normal cross section dated with radiocarbon and optically-stimulated luminescence (OSL) ages. The cores consist of a thick (> 20 m) subtidal mud from the base of the Holocene unit to the level of 3–4 m deep below the ground level, overlain by carbonaceous, intertidal mud. Chronological data reveal major episode of subtidal mud aggradation from 6 to 3.5 ka, forming the topography for mangrove development. Radiocarbon ages in the overlying intertidal mud range from 4 ka to modern and show some inconsistencies with the stratigraphy, suggesting mangrove root penetration and sediment mixing. The beach-ridge structure and OSL ages of the Can Gio barrier indicate that barrier formation initiated just before 3.2 ka. The transition from subtidal to intertidal mud aggradation and initiation of barrier formation, are broadly correlated with the onset of the subaqueous delta progradation and shift to a wave-dominated regime in the central delta. However, after 3.5 ka, the Can Gio shoreline had negligible sediment accretion while the central delta prograded up to 50 km seawards. Reduced sediment supply to Can Gio is consistent with more asymmetric, southwestward-dominated longshore drift after 3.5 ka. The negligible progradation at Can Gio also indicates minor sediment supply from the nearby Dong Nai River, which prevented upper intertidal accretion and translation of mangroves into a flood plain.
•Sedimentary evolution of the Can Gio mangrove, the NE margin of the Mekong delta, is constrained.•A thick (> 20 m) deltaic mud aggraded from 6 to 3.5 ka before the mangrove was initiated.•Sediment supply has been limited after 3.5 ka to allow the mangrove to persist.•The mangrove evolution reflected the morphodynamic feedback of the growing Mekong delta.
We performed the measurements of electrical resistivity (ρ) and dc magnetization (M) as a function of temperature (T) under pressure to investigate whether or not the superconductivity is induced by ...the application of pressure in lightly doped RFeAsO1-xFx (R=Sm and Nd) using pulse current sintered (PCS) high density polycrystalline specimens. We have successfully observed pressure induced superconductivity with Tc of ∼6 K (∼8 K) above ∼4 GPa (∼1 GPa) for R=Sm (R=Nd). An anomaly corresponding to a magnetic phase transition into spin density wave (SDW) state was observed in the ρ(T) curves in the entire pressure range, indicating that the superconducting and SDW states coexist in the T-P phase diagram. Volume fraction of the superconductivity is found to be very small. This is consistent with the coexistence of the superconducting and SDW phases.
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